Electrodeposition of metals



Patented Apr. 23, 1940 UNITED ST AT-ES PATENT OFFICE ELECTBODEPOSETION OF METALS Rudolf Lind, Euclid. William J. Harshaw. Shaker Heights, and Kenneth E. Long, South. Euclid, Ohio, assignors to The Harshaw Chemical Company, Elyria, Ohio. a corporation of No Drawing. Application December 14, 1939.

Serial No. 309,232

17 Claims.

" producing the above-named desirable characteristics in the nickel plate and which may be used with acid nickel baths of usual composition crating under usual conditions.

In order to properly evaluate the present invention, it is necessary to define brightness and ductility or brittleness, terms used in the old art,

Brightness It is obvious that an extremely thin deposit of nickel over'a highly buifed surface will appear bright. Bright plates of this type have been made for years and are well recognized .in the art. Their limitations are that if the plated article is exposed to the atmosphere or to wear, the plate soon disappears or wears off. A plate thin enough so that it will retain substantially the full brightness of the polished base metal is impractical for use even as a base for the electrodeposition thereover of a protective coating of other metals such as chromium. If a heavier deposit is plated out. the brightness of the highly buffed surface diminishes and a gray or white dull deposit is obtained.

A nickel plate which is thick enough to be practical for use and which is bright without buffing is not only desirable per se, but it is particularly advantageous where it is destined for use as the base for an electrolytically deposited chromium plate, since, if the nickel plate does not require to be polished and buffed, a relatively thin plate gives the same protection as the neces-- sarily heavier gray plate, some of which must be taken off in the polishing to secure the desired brightness. Furthermore, a very considerable saving in time and in cost on the production of plated articles becomes possible, whether with nickel plate per se or with additional chromium finish.

Various so-called addition agents have been proposed from time to time for inclusion in nickel plating baths in order to control or affect the character of the electrolytically deposited metal. One principal objective in such modification of the plating bath has been to increase the brightness or luster of the deposited metal.

Many of these previous nickel plating addition agents have allowed a much heavier-deposit of nickel to be built up before the brightness of the base metal was materially diminished. When polished articles are plated in such baths, the deposit is not truly bright but merely, at best,

OD- I (Cl. 20414) I has the same character as the base metal. The

brightness produced by such addition agents may, therefore, be characterized as brightness diminishing with increased thickness 'of plate on a polished surfacey r Others of these previous nickel plating addition agents have produced a plate which would maintain the brightness of the polished base surface, even though the plate was built up to a substantial thickness. They would not build up any substantial brightness on an unpolished sur- -face and, at best, would only very slowly build up brightness on an unpolished surface when plates of extreme thickness were made. The brightness produced by such addition agents may, therefore, be characterized as brightness maintaining itself with increased thickness of plate on a polished surface.

The addition agents of the present invention produce a plate that not only maintains the brightness of the most highly polished base metal, irrespective of the thickness of the plate within practical limits, but also increases in brightness with increase in thickness of the plate on an unpolished surface. .The brightness produced by such addition agents may, therefore, be characterized as brightness increasing with thickness of plate on an unpolished surface.

' 1 Dwctility The question of ductility is one of vital concern to the plater. In general, all bright plates are harder and, therefore, more brittle than ordinary dull nickel. When enough of many of the previously employed addition agents was added to a bath to produce a bright plate. the plate was often too brittle for commercial use and yet if less addition agent was used, the plate would not of brightness, but also with a high order of ductility as defined by the above scale. This is desirable and essential to the practical use of bright nickel plating.

The principal object of the present invention, therefore, broadly stated, is to provide an improved process of and materials for use in the process of electrodepositing nickel which will not only render the nickel plate desirably bright but which will also preserve or render the plate desirably ductile.

Broadly stated, our invention comprises the discovery that by the use in acid nickel electrolytes of a plurality of addition agents respectively selected from certain different classes of compounds, we are able to produce deposits which are superior to those,:obtainable by the use of addition agents from either one of such classes alone. We find that the addition agents: from one of said classes, although characterized by an embrittling tendency, are productive of extreme brightness when used in combination with addition agents from the other class and that addition agents from said other class not only cooperate in the production of brightness but also exert a ductilizing effect in the combination. The use of one addition agent from each class is preferable but a plurality from each class can be used successfully. Our cooperating addition agents are suitable for use in a wide variety of nickel electroplating solutions. We have found them to be very effective in aqueous acid nickel sulfate solutions and aqueous acid nickel chloride solutions. Among the nickel sulfate solutions in which they are effective are aqueous acid solutions of nickel sulfate, .nickel sulfate and nickel chloride, nickel sulfate and sodium chloride, nickel sulfate and hydrochloric acid, nickel sulfate and ammonium chloride, nickel sulfate and. alkali metal chlorides other than sodium chloride, the chlorides serving to produce good anode corrosion. Our addition agents are effective in nickel chloride solutions with and without nickel sulfate. In each of said solutions it is desirable, although not necessary, to employ boric acid or another suitable buffering agent. We may employ soluble or insoluble anodes. We prefer to employ a bath containing nickel sulfate together with a suitable chloride, preferably nickel chloride and a suitable bufier, preferably boric acid. We prefer to employ one or more addition agents from one of said classes in quantity to producev the desired brightness and one or more from the other class in quantity to overcome to a substantial extent the resulting embrittling tendency.

As representative of separate classes of compounds which, when used in combination as above stated, produce improved results, are those classes of compounds which may be respectively identified as (1) the amino poly aryl methanes in which at least one amino group is connected to an aryl group; and (2) the naphthalene sulfonates. Since these classes of compounds are in themselves distinct, it is believed advisable to deal with them separately in more specifically identifying them and in pointing out specific examples which will be found to be particularly suitable for use.

Amino compounds While this class of compounds has been identifled above as the amino aryl methanes, nevertheless, our invention contemplates for use as this group of addition agents compounds characterized by the presence of the primary, secondary or tertiary amino group; a large cyclic molecule and the dominance of the amino group or groups over other antagonistic groups.

A representative class of the above identified amino compounds are the amino substituted poly aryl methanes. The various substitution products of the poly aryl methanes which are within the contemplation of the invention may be classified as follows, vi z.:

The alkyl groups which may be present in certain of the above classes of compounds include methyl, ethyl, etc. The additional aryl groups which may characterize certain of the above mentioned sub-classes of compounds are the benzyl, phenyl, tolyl, etc.

The salts of the above referred to types of compounds, such as chloride, hydrochloride, acetate and sulfate, are preferable to the referred to type of compounds themselves because of their greater solubility. The reductlon products and carbitols of such compounds are also suitable and, in some cases; somewhat superior to the compounds themselves.

Specific examples which have been found to give good results are as follows, the common name and the chemical name from Farbstoif Tabelen by Gustav Schulz, 7th'edition, vol. 1 (1931), being given, where possible, as more specific, the particular salt employed being indicated in the following table:

TABLE I Triphenylmethane derivatives 1. pp Diamin'o m methyl fuchsonimonium chloride (Fuchsin).

2. Triaminotolyl diphenyl methane hydrochloride (reduction product of Fuchsin).

3. Triaminotolyl phenyl carbitol hydrochloride (carbitol product of Fuchsin) 4. Mixture of reduction products and carbitol of Fuchsin prepared as hereinafter explained.

5. Symmetric tetramethyl-p-aminofuchsonimonium chloride (Malachite Green).

6. Symmetric diethyl di p sulfobenzyl p aminofuchsonimonium sulfonate (sodium salt of internal sulfonate, Pontacyl Green 13).

7. Pentamethyltriaminotriphenyl methane acetate (reduction product of Methyl Violet).

8. Pentamethyl p.p diaminofuchsonimonium chloride (Gentian violet) 9. Hexamethyl p. p .diaminofuchsonimonium chloride (Crystal Violet).

Diphertylmethane derivatives 10. diphenyl It will be observed that all of the specific examples of triphenylmethane derivatives given above are fuchsonimonium compounds, thus more specifically identifying a class of compounds which has been found to produce remarkably improved plates when employed as a constituent in the bath comprising our invention.

We have found it most practical to prepare specific Example 4 given above in the following way: Fifty parts of the dye, 1,000 parts of water, 100 parts of granular nickel and 100 parts of hydrochloric acid are heated and mechanically stirred until the magenta color of fuchsin has practically disappeared. The mixture is then stirred with a small amount of activated carbon and filtered. The filtrate is made up to one liter and. contains the equivalent of five grams of the original iuchsin per 100 cc.

While the quantity of these substances employed is not sharply critical, they are used in small amounts, that is, amounts on the order of 2 to 100 milligrams per liter of theloath, the upper limit being determined by their embrittllng eifect and in some cases, their solubility.

Most of the specific examples given in Table I are commercial products. There are many other members of the same groups, mostly not 0011111181"- cial products or not obtainable in pure form, which we believe would, if available and sufiiciently pure, have the same effect. In general, impurities are undesirable Fuchsin and its carbitol and reduction products, prepared as above indicated, and 2.2,i.4'-tetramino 5.5'-dimethyl diphenyl methane produce plate of outstanding quality as compared with any of the other compounds listed. .l'he presence of the primary, secondary or tertiary amino group, the large cyclic molecule and the dominance of the amino group or groups over any antagonistic groups are be lieved to be the significant factors which account for the improved results.

The naphthalene sulfa notes l. itlpha naphthalene mono-sulfonate it. theta-naphthalene mono-sulfonate it. Naphthalene disulfonates l. Naphthalene trisulfonates ii. Sulionated naphthalene Specific Example of Table II above is such as may be produced by reacting 2 parts of 20% oleum on one part of naphthalene at 160 C. for two hours, neutralizing the resulting mixture with nickel carbonate, filtering and diluting to 26 Be. Where quantities of sulionated naphthalene are referred to hereinafter, it is to be understood that the quantity specified represents roughly the nickel-naphthalene-mixed-sulfonate content of the mixture. Five cc. of the nickel neutralized reaction mixtureis taken as equivalent to one gram of nickel-naphthalene-mlxed sulfonates. Except for solubility limitations or other purely physical considerations, it appears to be immaterial whether the named sulfonates are added to the bath as free acids or salts. It is usually preferable to add the nickel salts to avoid introducing foreign alkali into the bath. It is to be under stood that the addition agents of this second class, as well as the first, must haye adequate solubility in the nickel bath. They need not. however, be highly soluble therein since small quantities only are used as indicated in particular examples given below, In the selection of a sulphonic acid suitable for this use it seems best to choose those which are as free as possible from colloidal organic material present as impurities formed during the sulphonation, which has a brightening and embrittling eflfect on the deposited nickel. These sulfonates may be used in Various quantities upwards from gram per liter, however, 5 grams per liter or less is usually a sufficient concentration for best results. Larger quantities, within the limits of solubility, do no harm. I

A conventional acid nickel bath in which the combined. use of the two classes of addition agents will be found to give improved results, as above indicated, consists of;

NlSOtfiI-IsO lac-sac grams per liter.

NiC12.6HzO* lit-"l5 grams per liter.

H3803 lfiagrams per liter to saturation.

Sodium lauryl sulfateil-ZLO gram per liter.

Current density Up to 60 amperes per sq. it.

Temperature Room-170 i Whoi-e this compound is referred to, the material solo under the trade name of Duponol M. E. Dry is to be understood. It is sold as the technical compound. Other equivalent surface tension reducing agents ma be used instead of Duponol. Preparations known as ergitol 4.

and Tcrgitol 08, sold by Carbide (in Carbon Chemicals Co. and said to be sodium secondary alcohol sulfates, may be used instead of Duponol. The quantities required are of the some order.

Some hcptahydrate is usually present. Where nickel sulfate is used herein in specific exampleo, this mixture i of hydrates is to be understood.

PARTICULAR EXAMPLES Example N0. 1

Nickel sulfate grams per liter 240 -Nickel chloride do- 37.5 Boric acid do 37.5 Sodium lauryl sulfate.; ..do .25 Reduced Fuchsin do 0.005 Sulfonated naphthalene (nickel salt) do 4.0

pH 3.5 Temperature C i545 Current density amp./sq.ft 20 *That is, the reduction product of .005 g. of the unreduced dye.

Example No. 2

Nickel sulfate grams per liter 240 Nickel chloride do 37.5 Boric acid -i "do..." 37.5 Sodium lauryl sulfate do .25 Pontacyl Green B do 0.1

"Sulfonated naphthalene" That is, the reduction product of 0.005 g. of the unreduced dye.

Example No. 4

Nickel sulfate grams per liter 240 Nickel chloride do 37.5 Boric acid do 3:7.5 "Sulfonated naphthalene (nickel salt) v do 4.0 I 2.2, 4.4'-tetramino-5.5-dimethyldiphen-,

ylmethane sulfate grams per liter .010 Temperature C 45-47 Current density a amp./sq.ft 36 pH 3.5-4.5

Example No. 5

Nickel sulfate grams per Men. 240 Nickel chloride do 37.5 Boric acid ..do- 37.5 Sodium lauryl sulfate do .25 Reduced Fuchsin do .002 Mixture of alpha and beta naphthalene monosulfonates (free acid) do 2.0 pH 3.0 Temperature C 55-65 Current density amp./sq.ft 40 That is, the reduction product of .002 g. of the unreduced dye.

Emample No. 6

Nickel sulfate grams per liter 240 Nickel chloride do 37.5 Boric acid do 37.5 Sodium lauryl sulfate do .25 Reduced Fuchsin do .010 Sulfonated naphthalene" (nickel salt) do 4.0 pH 2.0 Temperature C 55-65 Current density amp./sq.ft 40 This application is a continuation-in-part of Lind et al., application Ser. No. 200,120, filed April 5, 1938, which is now abandoned.

Having thus described our invention, what we claim is:

1. An electroplating solution comprising an aqueous, acid solution of a nickel electrolyte of the class consisting of nickel sulfate and nickel chloride, said solution having the capability of producing bright and ductile deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being an amino poly aryl methane compound in which at least one amino group is attached to an aryl group and the other of said addition agents being a naphthalene sulfonate.

2. An electroplating solution comprising an aqueous, acid nickel sulfate solution having the capability of producing bright and ductile .deposits of nickel, such capability having been imparted thereto by the inclusion therein of cooperating addition agents, one of said addition agents being an amino poly aryl methane compound in which at least one amino group is attached to an aryl group and the other of said addition agents being a naphthalene sulfonate.

.3. An electroplating solution as defined in claim 2, such solution also having the capability of producing good anode corrosion, this latter ca pability having been imparted thereto by the inclusion therein of one or more substances of the class consisting of nickel chloride, ammonium choride, hydrochloric acid and alkali metal chlorides.

4. An electroplating solution as defined in claim 2, such solution also having the capability of producing good anode corrosion, this latter capability having been imparted thereto by the inclusion therein of one or more substances of the class consisting of nickel chloride, ammonium chloride, hydrochloric acid and alkali metal ch10- rides, said solution also containing boric acid.

5. An electrodeposition bath comprising an aqueous acid solution of nickel sulfate and nickel chloride and cooperating addition agents, one of said addition agents being an amino poly aryl methane in which at least one amino group is connected to an aryl group and another being a naphthalene sulfonate.

6. An electrodeposition bath as recited in claim 5 furthercharacterized in that there is added a quantity of an alkyl sulfate containing more than 6 carbon atoms sumcient to reduce the surface tension to below 50 dynes per centimeter.

7. The method of electro-depositing nickel which comprises electrolyzing a solution containing nickel sulfate, nickel chloride and boric acid and to which has been added both a substance of the group consisting of carbitol of fuchsin, fuchsin and reduced fuchsin, 2.2, 4.4-tetramino 5.5- dimethyl-diphenyl methane, and chlorides, hydrochlorides, acetates and sulfates thereof, and a substance of the group consisting of naphthalenemono sulfonates, naphthalene disulfonates, naphthalene trisulfonates and mixtures thereof, said solution also containing a minor amount of a sulfate of a normal primary aliphatic alcohol having at least six carbon atoms.

8. An electrodeposition bath comprising:

NlSO4.6HzO 120-450 grams per liter N1C12.6H2O -75 grams per liter H3303 15 grams per liter to saturation Amino poly aryl methane 2-100 milligrams per liter gram per liter to saturation said amino poly aryl methane being a substance of the group ccmsisting of carbitol of fuchsin, fuchsin, reduced fuchsin, 2.2, 4.4'-tetramino 5.5-dimethyl-diphenyl methane, and chlorides, hydrochlorides, acetates and sulfates thereof, and said naphthalene sulfonate being a substance of the group consisting of mono-, diand tri-sulfonates and mixtures thereof.

9. An electrodeposition bath as recited in claim 8, further characterized in that it-contains an aliphatic alcohol sulfate of at least six carbon atoms in quantity to reduce the surface tension below 50 dynes.

Naphthalene sulfonate /2 10. A method of electrodepositing nickel comprising eiectrolyzing an aqueous acid solution containing nickel sulfate, nickel chloride and boric acid as the principal constituents and cooperating .addition agents, soluble in the bath, of each of two classes, one of said classes of addition agents consisting of carbitol of fuchsin, fuchsin, reduced fuchsin, 2.2'-, 4.4'-tetramino 5.5'-dimethyl-diphenyl methane and chlorides, hydrochloride-s, acetates and sulfates thereof, the other of said classes of addition agents consisting of naphthalene mono, diand tri-sulfcnates and mixtures thereof.

11. A method as recited in claim 10 wherein the addition agent of the first defined class is maintained in the solution in quantity, not exceeding 100 mg. per liter, to produce enhanced brightness and the addition agent of the second defined class is maintained in the solution in quantity sufficient to'render the deposit ductile.

12. A method as recited in claim 10 wherein the addition agent of the first defined class is maintained in the solution in quantity from 2 to 10 mg. per liter, sufficient to produce enhanced brightness and the addition agent of the second defined class is maintained in the solution in quantity, not exceeding ,5 grams per liter, sufficient to render the deposit ductile.

13. An electrodeposition bath for the production of mirror bright and ductile deposits of nickel, the same containing per liter, approximately, nickel sulfate corresponding in quantity to from 120 to 450 grams of N1SO4'6H20, nickel chloride corresponding in quantity to from to 75 grams NiClz-GHaO, and cooperating addition agents as follows: (1) one or more compounds of the class consisting of carbitol of fuchsin, fuchsin, reduced fuchsin, 2.2-, 4.4'-tetramino 5.5'-dimethyl-diphenyl methane and chlorides, hydrochlorides, acetates and sulfates thereof in quantity from 2 to 100 milligrams, and (2) one or more compounds of the class consisting of naphthalene mono-, diand tri-sulfonates in quantity from V; gram to saturation.

14. An electrodeposition bath for the production of mirror bright and ductile deposits of nickel, the same containing per liter. approximatoly, nickel sulfate corresponding in quantity to from 120 to 450 grams of NIBOrGHzO, nickel chloride corresponding in quantity to from 15 to 75 grams NiClaBHaO, and cooperating addition agents as follows: (1) reduced fuchsin in quantity from 2 to 100 milligrams, and (2) one or 5 more compounds of the class consisting of naphthalene mono-, diand tri-sulfonates in quantity from /g gram to saturation.

15. An electrodeposition bath for the production of mirror bright and ductile deposits of i0 nickel, the same containing per liter, approximately, nickel sulfate corresponding in quantity to from 120 to 450 grams of NiSOrGI-IsO, nickel chloride corresponding in quantity to from 15 to 75 grams NiCl2-6H2O, and cooperating addition 15 agents as follows: (1) fuchsin in quantity from 2 to 100 milligrams, and 2) one or more compounds of the class consisting of naphthalene mono-, diand tri-sulfonates in quantity from A; gram to saturation.

16. An electrodeposition bath for the production of mirror bright. and ductile deposits of nickel, the same containing per liter, approximately, nickel sulfate corresponding in quantity to from 120 to 450 grams of NiSOrGHzO, nickel chloride corresponding-in quantity to from 15 to grams NiClz-8Ha0, and cooperating addition agents as follows; (1) carbitol of fuchsin in quantity from 2 to milligrams, and (2) one or more compounds of the class consisting of so naphthalene mono-, diand tri-sulfonates in quantity from gram to saturation.

17. A method of electrodepositing nickel comprising electrolyzing an aqueous acid solution containing nickel sulfate and nickel chloride as the principal constituents and cooperating addition agents, soluble in the bath, of each of two classes, one of said classes of addition agents consisting of carbitol of fuchsin, fuchsin, reduced fuchsin, 2.2"- g1.4'-tetramino 5.5'-dimethyl-diphenyl methane and chlorides, hydrochlorides, acetates and sulfates thereof,the other of said classes of addition agents consisting of naphthalene mono-, diand tri-suifonates andmixtures thereof.

RUDOLF LIND.

WIILIAM J. HARSHAW. KENNETH E. LONG. 

